Agitator

ABSTRACT

For agitation-that is, either for grinding or for mixingsubstantially spherical agitating elements are kept in a state of continuous agitation by means of an agitator formed of a vertical shaft with arms attached tangentially to the shaft. The arms may be straight or curved. Usually the arms are so attached that the distance from the point of attachment to one end of the arm is several times the distance from the point of attachment to the other end of the arm.

United States Patent Andrew Szegvari 201 Castle Blvd., Akron, Ohio 44313650,392

June 30, 1967 Oct. 12, 1971 Aug. 9, 1966 Great Britain inventor Appl.No. Filed Patented Priority AGITATOR 2 Claims, 5 Drawing Figs.

U.S. Cl 241/172 Int. Cl 1302c 17/16 Field of Search 51/7; 241/172;259/134-137 References Cited UNITED STATES PATENTS 1/19g) l(lock.

Wulftange 259/136 Jones 259/107 Lodige. 241/172 X Rand 259/136UX Wadham241/172 Primary Examiner-Harold D. Whitehead Attorney-Gordon C. MackABSTRACT: For agitation-that is, either for grinding or formixingsubstantially spherical agitating elements are kept in a state ofcontinuous agitation by means of an agitator formed of a vertical shaftwith arms attached tangentially to the shaft. The arms may be straightor curved, Usually the arms are so attached that the distance from thepoint of attachment to one end of the arm is several times the distancefrom the point of attachment to the other end of the arm.

PATENTEDUETIZISYI w 3.612.419

, sum 10F 2 F'TUIIEL l l l INVENTOR $4M BY WfM ATTORNEY PATENIED001121971 3,612,418 SHEET 2 OF 2 INVENTOR QM 4% ATTORNEY This inventionrelates to a device for agitating balls in a ves-- sel, the balls beingsubstantially spherical and all being of substantially the same size. Anovel agitator is used, which comprises a vertical shaft to which armsare attached. Although usually a cylindrical and erect vessel is usedwhich contains but a single agitator, the vessel may comprise two orthree or more agitators. The device is used primarily for grinding,usually in a liquid medium, but it may be used for agitation as for themixing of immiscible liquids.

The agitator is operated at such a speed as to impart kinetic activationto the balls so that they are kept in a state of continuous agitation,contacting one another and the wall of the vessel, with no more than asmall portion of the balls contained in a relatively quiescent state inthe bottom of the vessel.

It has been previously proposed to use for this purpose an agitator inwhich the arms pass through the vertical shaft. It has also beenproposed to attach to the vertical shaft a series of annular ringslocated eccentrically with respect to the shaft, with the rings securedby spacing rings located around the shaft, and the adjacent rings atdifferent angles of eccentricity with respect to one another.

There are a plurality of arms attached to the shaft of this invention,and although generally the arms are straight, they need not necessarilybe straight although they are not continuous as in a circle, but haveexposed ends. It has been found that by attaching the arms tangentiallyto the shaft, more efficient agitation is obtained than if the arms passthrough the center of the shaft. Moreover, it has been found that theagitator of this invention is more efficient than the agitator in whichrings are located eccentrically about the shaft.

Usually in attaching the arms to the shaft, either each arm or theshaft, or both, will be indented so that the arm fits snugly against theshaft, and it is preferable to attach the arm to the shaft by means suchas one or more screws which pass through the shaft into each arm ratherthan passing a screw or the like through the arm and thence into theshaft, because the latter tends to weaken the arm.

Although the arms may be attached symmetrically to the shaft so that thesame length of arm extends outwardly from each side of the point atwhich the arm is fastened to the shaft, it is preferable to have theends of the arms asymmetrical. In a preferred arrangement the arms areattached so that the distance from the point of attachment to theportion of the arm projecting in one direction is several timessuch as 1wt to three times-the length of the arm projecting in the otherdirection from the point of attachment. In this situation it ispreferable to have the shorter portion of the arm pointed at its end andto have the end of the longer portion of the arm enlarged.

As an alternative arrangement, the arms need not be straight but theends may curve somewhat as, for example, by having one end curveslightly in the direction toward the shaft and the other curvingslightly in the opposite direction.

The arms may be circular in cross section or they may be oval,rectangular or diamond shaped, but preferably have cross sections theshape of a teardrop with the pointed portion pointing in the directionopposite the direction in which the shaft is rotated. If the arms arerectangular in cross section, it is preferable to have the horizontaldimension the larger dimension.

Although it is possible to have two or perhaps three of the armsfastened to the same cross-sectional area of the shaft, it is preferableto stagger the arms so that on rotation the volumes of the contents ofthe vessel through which they pass do not overlap.

An agitator may, for example, be 8 or 10 or more inches in length andwill usually be no greater than one-half to 3 inches in diameter. Thearms may each measure about one-fourth to one-half of a square inch incross-sectional area. Such an agitator and a vessel measuring 36 incheshigh and about 9 inches in diameter with arms which are of the samecross-sectional area throughout but fastened to the shaft at a locationnearer one end of each arm than the other, with the agitator operatingat a speed of 300 to 1,000 rpm. will give efficient agitation.

The invention is further described in connection with the accompanyingdrawings, in which FIG. 1 is a vertical view of an agitator and grindingmedia in a vessel, shown in phantom;

FIG. 2 is a top view of a different agitator, showing the shaft insection;

FIG. 3 is a vertical view of an agitator shaft and arm shown in section,illustrating the preferred method of attachment of the arm to the shaft;

FIG. 4 is a section through a shaft with a modified arm attachedthereto; and

FIG. 5 is a section through a shaft with still a different arm attachedthereto.

In FIG. 1 the shaft 5 is located vertically in the cylindrical vessel 7and the shaft is rotated about its axis by driving means (not shown).Arms 8 are attached at their midpoints to the shaft. Only four arms areshown although in practice the arms may be staggered over the entirelength of the shaft. The vessel includes grinding media 9.

FIG. 2 shows a horizontal section through shaft 10 to which four arms11, staggered along the length of the shaft, are attached. Theattachment is not at the midpoint of the arms. The shaft is preferablyrotated in the direction of the arrow.

FIG. 3 illustrates a preferred method of attaching an arm 15 to shaft16. The screw 17 passes through the shaft, but does not pass entirelythrough the arm because this would weaken it.

FIG. 4 is a top view of a shaft 20 to which is attached the arm 21 whichis of circular cross section throughout its length. It is pointed at itsforward end and its rear end is of increasingly larger diameter than itsmain portion.

FIG. 5 is a top view of a shaft 25 to which is attached the arm 26. Asthe arm is rotated it travels in a horizontal plane. Its forward endflares away from the shaft and its rear end is bent toward the shaft.

I claim:

1. An erect cylindrical vessel with a height at least four times thediameter which vessel contains substantially spherical grinding elementsall of substantially the same size and is equipped with an agitatorrotatable about its axis, with means for rotating the agitator at asufficiently high rate of speed to impart kinetic activation to thegrinding elements so that substantially all of them are kept in a stateof continuous activation, said equipment being characterized by the factthat the agitator is composed of a vertical shaft having arms foractivation of the grinding elements tangentially attached directly toit, each arm having its opposite ends exposed and being attached to theshaft at only one location, the respective ends of the arm being ofsubstantially different cross sections so that the outlines of theliquid displaced thereby are substantially different.

2. An erect cylindrical vessel with a height at least four times thediameter which vessel contains substantially spherical grinding elementsall of substantially the same size and is equipped with an agitatorrotatable about its axis, with means for rotating the agitator at asufficiently high rate of speed to impart kinetic activation to thegrinding elements so that substantially all of them are kept in a stateof continuous activation, said equipment being characterized by the factthat the agitator is composed of a vertical shaft having arms foractivation of the grinding elements tangentially attached directly toit, each arm having its opposite ends exposed and being attached to theshaft at only one location, the forward end of most arms is pointed andthe rear end is bluntly enlarged.

1. An erect cylindrical vessel with a height at least four times thediameter which vessel contains substantially spherical grinding elementsall of substantially the same size and is equipped with an agitatorrotatable about its axis, with means for rotating the agitator at asufficiently high rate of speed to impart kinetic activation to thegrinding elements so that substantially all of them are kept in a stateof continuous activation, said equipment being characterized by the factthat the agitator is composed of a vertical shaft having arms foractivation of the grinding elements tangentially attached directly toit, each arm having its opposite ends exposed and being attached to theshaft at only one location, the respeCtive ends of the arm being ofsubstantially different cross sections so that the outlines of theliquid displaced thereby are substantially different.
 2. An erectcylindrical vessel with a height at least four times the diameter whichvessel contains substantially spherical grinding elements all ofsubstantially the same size and is equipped with an agitator rotatableabout its axis, with means for rotating the agitator at a sufficientlyhigh rate of speed to impart kinetic activation to the grinding elementsso that substantially all of them are kept in a state of continuousactivation, said equipment being characterized by the fact that theagitator is composed of a vertical shaft having arms for activation ofthe grinding elements tangentially attached directly to it, each armhaving its opposite ends exposed and being attached to the shaft at onlyone location, the forward end of most arms is pointed and the rear endis bluntly enlarged.